This invention relates to a method and apparatus for recovering and recycling condensable reactants in a chemical process, particularly those used in the manufacture of semiconductor chips.
Until recently, compounds of noble gases, such as helium, neon, argon, xenon and krypton were considered impossible to achieve. When they were initially discovered, they were considered to be only scientific curiosities. Only recently has it been discovered that these materials can be useful in solving difficult problems encountered in the fabrication of semiconductor devices. For instance, in U.S. Pat. No. 4,190,488 by Harold F. Winters a method for using noble gas halides, particularly XeF.sub.2, as an etchant for silicon and various metals is described. This method has particular advantages for the production of high density semiconductor arrays used in advanced information handling technology. The noble gas halides are very expensive compounds. Therefore, it is desirable to recover any of the noble gas halide that is unreacted for reuse. To make effective reuse of an unreacted noble gas halide the reaction products from the etching process must be separated out.
There are many chemical processes which would benefit from a method of recovering expensive or toxic reactants. A further example from the semiconductor manufacturing industry are processes for depositing silicon onto a semiconductor device. Silane (SiH.sub.4) is an expensive reactant used in this process. By recovering and reusing unreacted silane the costs of manufacturing can be reduced. Another process that would benefit from the recovery of reactants is the production of helium arsenide. Arsine is a toxic reactant in this process which is often disposed of when unreacted. The ability to recycle unreacted arsine would provide a more efficient production process.